Nightlings
Overview
Nightlings are birdlike humanoids: digitigrade, winged, feathered, and clawed. They have black, slightly iridescent feathers that cover the majority of their body, bluish-black skin, and white eyes. They spent most of history underground, as they are native to the extensive cavern systems that spans the central portion of the continent. Sometimes called shadowlings or aveoliths, their unfamiliarity and unfortunate timing of first contact has made them the subject of varying degrees of hostility by sunlings.
A female nightling is a hen. A male nightling is a crow.
Evolution
Nightlings began, in very very early evolutionary history, as an offbranch of early griffons. This ancestor, significantly more reptilian than modern griffons, was social and raptorial, unlike what would become extant griffons, which are quadripedal. This griffonoid ancestor bore no genetic relation to other humanoids, but mimicked them over time for one simple purpose: nightling ancestors were prey animals, and proto-humanoids were predators. In this way, the griffonoid ancestor adopted a more humanoid form- upright stance, long arms, hands, humanoid faces, vocalization.
Because nightlings evolved from a transitional species, they have features of both reptiles and true birds. They are warm-blooded, feathered, and social, with three-toed feet and hollow bones. They lack beaks, however, instead having a reptilian jaw. Their lungs also function like that of birds'. In this way, they are not true birds, but rather bird-like reptiles. They are an extremely basal species.
This mimicry continued, and offbranches of the humanoid proto-nightlings began to inhabit other environments, notably, the rich, deep cave systems by the rift valley. These cavern proto-nightlings moved deeper and deeper until they were cut off from the surface, and the surface-dwelling branch went extinct. Thus the existence of nightlings faded from sunling knowledge, and the existence of sunlings, from nightling knowledge.
In the caverns, nightlings adopted a few adaptations to better suit them to their environment. Their coloration changed abruptly with the introduction of a hyperpigmentation mutation, resulting in black feathers and skin that allowed them to blend into the dark cave environment. Their eyes became hyper sensitive to light, because while light is present in the caves via bioluminescence (see Environments), it is dim and lacking. Their wings specialized, trading manuverability for compactness and lift, better to navigate caves that alternate between large, tall caverns and small, thin tunnels. Their feathers grew dense, protecting them from the chill of the caverns (nightlings aboveground are susceptible to heat, and have a reputation for being hardy in cold). They also shortened ever so slightly, again, better to navigate small, cramped spaces.
Taxonomically, nightlings could be considered dragons under certain definitions. They belong to the group that became dragons, same as griffons. Nightlings are dragons as much as griffons are, as you cannot include all dragons in a monophyletic group without either including griffons (and nightlings) or excluding some dragons. Interestingly, nightlings cannot be considered griffons under these same definitions, as griffons evolved from proto-nightlings' sister taxa, as such, their evolutionary lineages are distinct.
Physiology
Nightlings are theropods, evolved from raptorial ancestors. The majority of their bodies are covered in feathers- only the most distal portions of their limbs (from elbow/heel down), faces, and throats are uncovered. They have decorative1 plumage on their heads- the only example of sexual dimorphism in nightlings. Their wings have been hyperspecialized for compactness- as such, much of the muscle structure that supports them is ingrained among other bones and muscle groups. Nightlings have fossa and eminences in their ribs, collarbones and shoulderblades that house connection points for wing muscles, as well as a secondary set of pectorals responsible for wing movements. They lack a true tail- the only remains of their ancestors' tail being long feathers at the base of their spine.
Sexual Dimorphism
The only overt difference between a hen and a crow is that of the plumage. Even this is extremely subtle, and most sunlings cannot tell the difference between a male or female nightling, though most nightlings can. Both plumage types feature feathers that extend up and back from the skull, the longest feathers from the very back of the head, and the shortest beginning at the browline, bridge of nose, and sides of the face.
Hen's plumage is compact against their heads and serving the purpose with little flair. Their plumage feathers are usually thinner and longer on average. Hens typically also have a greater volume of feathers on their stomachs and thighs- this functions in their caretaking of fledglings, as they can be held safely in their lap to be kept warm, either to brood the egg or after the baby hatches.
Crows, however, sport a wider, broader variation on the female plumage, feather pattern beginning further down the jawline and forming a wreath-like shape around the head. Male plumage is less streamlined, exhibiting less of the 'slicked back' look present in female plumage, with shorter and wider feathers.
Nightlings are the least sexually dimorphic species, with no other differences than plumage.
Hyperpigmentation
Nightlings are hyperpigmented, meaning they have an abundance of pigment in nearly all of their cells. The only exception in their body is their eyes: which are believed to have remained white as a method of nonverbal communication with other nightlings in dark caverns where it may otherwise be difficult to spot one another (similar to the development of the white sclera in other humanoids).
Hypermelanism comes from an overexpression of the endothelin 3 gene, a gene that the vast majority of vertebrates have; it controls skin color. However, in hypermelanistic animals- nightlings included- this gene is expressed in almost every cell: even those that don't usually have pigment. As a result, nearly every tissue in a nightling's body is heavily pigmented, typically resulting in a blueish black color. This includes feathers and skin, but also muscle, organs, and bones.
Their teeth are white because teeth are not true bones: enamel is white, and is not made up of cells, so it cannot be affected by hyperpigmentation.
Vision
Their eyes are unlike any other humanoids' in that they have no iris or pupil.
In actuality, they have an iris similar any other sighted animal, and it actually takes up more space of the eye than other humanoids, but it is completely devoid of pigment, both on the surface and the backside. This allows light to shine through the actual tissue of the iris and be absorbed across a wider area than if it was restricted to only the pupil. The iris is also thinner than usual, just a few cell layers thick in the thinnest part, which allows light through easier. The blurring that would be expected from this method of sight, due to the light that is scattered by the covering, is 'filtered out' rather accurately by the brain, just like brains 'flip' the image the eye creates. Even so, nightlings do often have a minor form of nearsightedness inherent to their species- very large distances become hard to discern detail across.
Further, they have a pupil in the sense that there is a hole in the sclera of the eye, but it is completely covered by the tissue of the iris, leaving no discernable 'hole' where the pupil lies. Because of this, nightlings are unable to control the amount of light that enters their eyes, a problem that doesn't affect them in their natural habitats, but aboveground can prove to make daylight uncomfortable or even physically painful.
Nightlings also sport a tapetum lucidum along the back of their eyes, allowing them to better see in low-light conditions, with an added effect of giving them eyeshine. It is more reflective than the average nocturnal animal's because the caverns get significantly darker than nighttime on the surface ever does: nightlings' eyes are so reflective they functionally glow.
Nightlings are also dichromats: they lack the L-cones necessary to see red. There is little to no red naturally occurring in their caverns, as the only light comes from blue and green bioluminescent fungi and animals, so they lost their ability to see it.
Endosymbionts
Nightlings have no bioluminescence. They do, however, carry a mutualistic, single-celled eukaryotic endosymbiont in their bloodstream. This symbiont is luminescent.
The symbiont is transferred from mother to child as the egg develops before being laid, multiplying in the albumen before migrating inwards to the bloodstream. The symbionts feed off dead and dying cells in the bloodstream, as well as bacteria, phages, or other invading cells. In this way, the symbiont acts as a secondary immune system. Nightlings, then, are extremely resistant to disease and all but immune to infection.
This also means that there is a nonzero chance of unique autoimmune diseases that develop when the relationship between host cells and symbiont cells fails.
The first kind occurs when the symbionts no longer recognize the blood as 'friendly' cells, and they attack the nightlings' own cells. This disorder can be developed later in life as well as in the egg and is very rare, usually occurring under a stressor to the symbiont (something like high radiation levels that would increase mutation), and is usually deadly.
The second kind is survivable, and occurs when the nightlings' cells no longer recognize the symbiont as 'self.' This usually develops early in the egg, and has little effect on the nightling itself aside from a decreased immune system and blood that doesn't glow, as the host cells eliminate the symbionts.
The bioluminescence of the symbiont is speculated to result from its (probable) origins in fungal bodies. This luminescence serves two purposes: distraction and warning to predators, and communication of danger to other nightlings. Nightlings are, evolutionarily, prey species- bright blood acts the same as squid ink to predators; and a social species- it alerts companions that there is a wounded nightling in need of help and to be on the watch for danger.
Hatchlings
Nightlings are raptors: as such, they don't carry live young. Eggs are usually laid in just one per clutch- because of nightlings' relatively large size as birds, and the fact that they care for their young, it is more evolutionarily efficient to minimize energy cost in favor of a single, healthy fledgling.
Eggs are laid approximately two weeks after fertilization, and take an additional seven months to hatch. Nightling eggs are less than half a foot wide and up to a foot long. They are black, sometimes with lighter speckled patterns that help them blend in with the cavern walls and floors. Hatchlings grow nearly fully formed talons on hands, feet, and wings while still in the egg, as these are used to break the shell during hatching. These claws are usually trimmed by parents after hatching to prevent the baby from hurting itself.
Newly hatched fledglings are covered with downy feathers and quickly grow a coat of mature feathers as they age. Their wings begin to fill in at about 5 months of age, and at 6 months hatchlings can achieve some sort of lift- though it is still upwards of a year before they can begin to actually fly. When they start to walk, they often use this lift to remove some of the weight from their tiny legs, or to help balance.
Even as their wings grow flight feathers, fledglings stay downy on the majority of their bodies until about 7-8 years old, after which it starts to fade. Most nightlings are free of down by 11-12.
Instrinsic Behavior
Nightlings are not true nocturnal creatures: their natural sleep cycles don't follow the sun at all as a result of the lack of sunlight in caverns. However, nightlings' eyes are acclimated to the dark- in daylight, particularly on bright, sunny days, the light can be anywhere from uncomfortable to painfully bright, so most nightlings adopt nocturnal lifestyles for comfort.
What they are capable of though, as birds, is unihemispheric sleep. This allows them to catch light sleep while still staying alert for possible danger, but they remain capable of deep sleep as well, depending on the safety of their environment. If a nightling cannot afford to sleep completely unconscious, they require longer hours to reach the same restorative effects that deeper sleep would provide. A nightling that never gets the ability to sleep deeply can experience much of the same effects as a person who doesn't sleep long enough: in both cases, chronic fatigue is a real threat.
Vocalization
Nightlings differ from most other birds in that they have vocal structures more similar to dragons or mammals than birds: most modern birds developed the syrinx as a response to miniaturization from raptoroid ancestors, but since dragons, griffons, and nightlings didn't miniaturize, their vocalizations didn't require any adaptation. Nightlings don't 'sing' like birds, but rather their speech is somewhere between a controlled roar and the call of a corvid. There isn't an accurate external application for what a nightling's voice sounds like: they vocalize like dragons, though dragons use it louder, deeper, and less ordered. Nightlings are also capable of a hiss in the same way a dragon is: it's not feline, but reptilian.
That being said, their voices are higher and smoother on average than most other humanoids. Nightlings have no vocal differences between hens and crows, and while their voices are relatively high, they don't fall within the typical 'female' register of mammalian humanoids, but somewhere adjacent to it. They don't sound like women by nature of their pitch, rather, the timbre of their voices, while high, is a different sound by nature of being avian, and that is what makes them distinct from human women.
Culture
Timekeeping
Nightlings in the underland use a unique calendar, as a result of being separated from the sun, moons, and (mostly) the seasons.
Their years follow aboveground years, only because of the river: it is subject to yearly flooding coinciding with snowmelt and spring on the surface. But their shorter-term timekeeping, able to roughly translate to days, weeks, and months, are completely separate.
Days are roughly 10 hours long, counted in 12s. They are kept by the very regular life cycle of a certain species of fungus. It takes exactly 10 days to grow to maturity, on the 10th of which it glows to attract pollinators, spores, and dies by the 11th day. This species grows cap-like shelves each day, like tree rings, making it very easy to mark how old any single mushroom is2. On the 11th day, it ceases to glow and very quickly wilts, having used all its energy reserves to release its spores and exhibit that luminescence. By the 12th day, it falls to the ground.
Timepieces are carved into cavern walls, 13 plots arranged in a circle. The uppermost plot marks the current day, and the growth of the fungi in the plots keeps the date. Every day, a new piece is planted in the '0' spot, after 12 and before 1, and ensures a constant rotation of growth. One full rotation tracks a week. Spores are planted at the same spot (the upper left) at the beginning of each week, and proceed through the timepiece counterclockwise as the week progresses. The growth follows clockwise, and so the 'clock' is read clockwise, but this requires the planting to be done counterclockwise.
The 13th plot is considered unused and is not counted in the actual days that make up a week. It is the 13th in terms of counting numbers, but it is thought to be the 0th plot in terms of its place in the cycle. This is where new fungi are planted, but they are not yet visible until a day later.
Weeks are 12 days long. There are 12 weeks in a month, with the exception of the first month, which has 13. There are 6 months in a year.
As days are marked by the life cycle of the mushroom, they are awarded a connotation from where in that cycle they fall. These ideas follow nightlings through their lives, even those on the surface who may not be able to trace the belief to its origin.
10 is a lucky number, the largest the mushroom will grow, and the day it spends luminescent. 10 is implicative of good tidings and expected to bring fortune- not in wealth, but in prosperity, peace, and happiness. The 10th day of every week is lucky, and the 10th day of the 10th week of every month is a day of celebration- dancing and song. Hatchlings that do so on this day are considered good omens for the family and for themselves: they will live long, happy lives. Other ceremonies (weddings, rites, etc) are typically not held on this day, since there are already festivities held then, but often are held on 10th days for that same luck.
It is incredibly bad luck to hold a funeral on the 10th day. To do so sullies that good luck and invites a kind of karmic misunderstanding- by holding a funeral on a lucky day, you ask for more death by implying the funeral is a good omen.
11 is the number of death- the 11th day is the day the shelves wilt and die. It is unlucky, expected to bring ill will, misfortune, or bad news. The 11th day is, though, the ideal day to hold a funeral, to send off the dead in harmony with the living. The 11th day of the 11th week is a day of rest, no work taking place, no travel, essentially a hunkering down and waiting out the storm. No ceremonies are held on 11th days- to do so invites whatever is being celebrated to fail.
Every nightling has a day specific to them: 11 years, 11 weeks, and 11 days from their hatching. This day, known as their Auspice, is observed every 11 years throughout a nightlings' life. This day is a bad omen, bound to bring ill will and misfortune3.
12 is less often considered an omen in either direction than 10 or 11, but does hold significance for funeral rites. It is a hard taboo to hold a funeral on the 12th of the week, for the 12th day of the timepiece is empty. The old mushroom has shriveled, died, and fallen away, but nothing new is planted yet. In this way, holding a funeral on a 12th implies emptiness, a non-existence that prevents the dead from finding an afterlife. This is sometimes believed to damn them to a limbo state, not dead nor alive, but more often is believed to simply erase the soul of the deceased, preventing them from having any sort of continuation. Weddings and hatching rites (though hatching cannot be planned) are also not to be held on a 12th, lest the life of the involved party(s) be devoid of meaning, but none of this is as dire as a funeral.
Most months, of which there are 6, are 12 weeks long (144 days). The first month, however, is 13 weeks (156 days). The floods come in the first month, marking a new beginning with an abundance of fresh, rich water flowing through the caverns.
Large timepieces with a yearly calendar encircled around it are found in communal spaces and some homes. Days are marked off with swipes of luminescent fungi- slime molds, mostly, used as pigment that won't fade over the course of the year. At the beginning of a new year, they are all cleared away, making room for the coming days to be marked as they come and go. This yearly ritual is a celebration- new beginnings, old endings. Room for more life, the darkness reclaiming the time that has passed and calming the harsh glow that will have taken over the calendar by that time. It's a softer, more mellow state that will be chased into brightness once again with the coming year. The new year comes gentle, easy on the eyes.
Of course, some of the patches may have died by the year's end: some people replant them as the year progresses, keeping the passed days lit and the coming ones dark, but some let them fade, and at the end of the year, make summaries, predictions, or both, based on the days that have gone dark. It's like reading tea leaves, or drawing constellations, or seeing faces in wood.
Pendants
Every nightling wears a pendant made from the egg they hatched from for the duration of their life. The pendant is made, usually by a family member, most often a parent, very soon after hatching. Designs vary, but must be durable- as durable as eggshell can be. The mother wears her child's pendant until it reaches 12 years of age- then it is entrusted to the child for the duration of their life.
The pendant is kept until 10 because 10 is when the child reaches their first glow, a symbolic period of growth, prosperity, and wellness. This time makes them fit to hold their pendant- to keep it safe- but it is not awarded at 10. It is given at 12, because 11 is a deeply unlucky number, for lack of a better word. 11 is the number of death and, more broadly, misfortune. The pendant is kept from the child, then, until they reach 12 years of age and safely make it out of that dangerous number. Then, and only then, is the pendant bearing their life entrusted to their care.
Great care is taken to prevent the pendants from breaking. Edges are reinforced with wire, metal, or gloss; casts in glass, amber, copper; skeletons of metal and bone. But sometimes, they do break.
A broken pendant indicates something deeply wrong- only by great violence or great neglect does the eggshell crack. Pendants are seen as an extension of the individual's soul- a cracked one means something has escaped. A piece of the person has broken, too. They are repaired, of course, and the utmost attention is given to ensuring they stay that way, but by the nature of the material, it is impossible to invisibly repair. In this way, nightlings wear their lives over their chests.
On the 11th day of the 11th week of a nightling's life, every 11 years, they will entrust their pendant to a close confidant for the day. This isn't a responsibility to be taken lightly- it is, in all ways but literal, an entrusting of their very life to the holder of the pendant.
A nightling's first Auspice occurs before they are given their own pendant, and so is no consequence apart from being a particularly dangerous day for the child. Every 11 years after that, though, the nightling must choose who to trust their pendant to. A natural choice, if one exists, is a bonded partner. If not them, then a parent, or a sibling, if close, or a very, very close friend. This person has to be someone you trust your life with, and they must be willing to accept that responsibility, even if for just a day. Some elderly nightlings, when their partner has died, may entrust their pendant back to adult children on their Auspices. This is a token of high respect from parent to child, and is something the child will remain proud of for the rest of their life.
This is the only day a nightling will be seen without a pendant. A nightling missing their pendant- not on their Auspice- means something has gone very, very wrong.
Upon death, the individual's pendant is used as a grave marker of sorts. In the underground, the body is sent down the river, but the pendant is placed in a burial cave, usually on a geological feature, to mark a place of return. Aboveland, they are gravemarkers in a more literal sense, marking where the body is buried.